1. Field of the Invention
This invention is related to a personal dosimeter for registering gas contaminants in the atmosphere and to a gas diffusion device to be used therein. More particularly it is related to a self-contained dosimeter capable of integrating the exposure level of a gas contaminant over a given period of time.
2. Description of the Prior Art
In response to the increasing concern about the health of workers who are exposed to harmful pollutants in the air, it has become necessary to monitor the concentration of the air-borne contaminants. One development for this purpose involved a rather large air pump which would force air to be sampled through a filter, trapping particulate contaminants. This obviously is unavailing for the monitoring of gas contaminants and, even for particles, is not accurate to determine concentration of the particles in the sampled atmosphere.
Personal sampling devices which are worn by individual workers and which passively collect the contaminants have also been used. For example, a device which utilizes the molecular diffusion of the gas to be monitored to collect the sample has been described in American Industrial Hygiene Association Journal, Volume 34, pages 78-81(1973). This device, however, requires that the collecting medium be removed therefrom, and carefully treated with reagents which must be exactly-measured at each analysis. The disassembly of the device and use of cumbersome reagents required for each analysis are disadvantageous.
Other personal sampling devices have used membranes which are selectively permeable to the gaseous contaminant to be monitored. Behind the membrane is usually sealed an absorbing medium for the gas. After exposure, a reading is taken of the contaminant concentration in the medium which is relatable mathematically to the contaminant's average concentration in the atmosphere over the time of exposure. However, at high concentrations, these membranes pass too much of the gas and the correlation between the concentration in the absorbing medium and that in the atmosphere is destroyed.
Therefore, there remains a need for a personal gas contaminant dosimeter for gaseous contaminants which accurately integrates, that is, indicates the average concentration of the gaseous contaminant over a given time period, and which easily lends itself to analysis without removal of the gas-collecting medium or bothersom addition of other elements.